This invention relates generally to a CD and DVD read head optical system. The invention includes various configurations that combine CD and DVD reader optics into a monolithic moldable plastic assembly including a hollow plastic block which can be made better, faster and cheaper than current discrete component technology designs. The resultant read head optical system will be capable of reading either CD or DVD disks, and capable of writing CD-R disks.
The basic philosophy of the present invention is that optical coatings on plastic substrates (e.g. the dichroic combiner and the output/input beamsplitter) are difficult to produce and drive the cost to a level equivalent to independent component designs. Optical coatings in a solid plastic block would require bonding two plastic blocks together and this is as bad as the coating itself in terms of cost and labor investment. Therefore, square glass plates with the necessary optical coatings can be captured in a hollow plastic block with high alignment precision with low cost. Coating plastic surfaces is considered too risky and costly so coatings have been deposited on glass plates that. are inserted into molded plastic blocks which have integral molded lens surfaces and (in some cases) Total Internal Reflection (TIR) prism surfaces.
Four monolithic embodiments are disclosed. The first embodiment includes a 780 nm laser diode and a 655 nm laser diode with their output beams perpendicular to each other. Two entry surfaces are therefore required to be formed on the hollow plastic block. In the second embodiment, the output beams are parallel, with the 655 nm and 780 nm lasers side-by-side. Only one planar entry surface is required. The third embodiment is a system for use on laptop installations and having a low profile of 6 mm and a single planar entry surface. The fourth embodiment uses a multi-faceted diffractive combiner to merge two laser diode beams, which can be utilized in a low profile (6 mm) configuration for use on laptop installations.